Apparatus for providing protection against momentary loss of track circuit shunt



Sept.v 1, 1959 A. E. DODD APPARATUS FOR PROVIDING PROTECTION AGAINST MOMENTARY LOSS OF TRACK CIRCUIT SHUNT I Filed Sept. 16, 1957 INVENTOR. ArilzwrEf Dodd HIS ATTO NE! United States PatentQ "w poration of Pennsylvania Application September 16, 1957-, Serial No. 634,179 7 Claims. (31. 246-"-41.)

My'invention relates to railway track circuit apparatus. More particularly, my invention relates to track circuit apparatus for preventing improper operationof. railway trafiic controlling apparatus due to a momentary loss of track circuit shunt. p

The most commonly used method of detecting the presence of a railway /vehicle in a section of railway track is to provide the section with an electrical circuit commonly called a track circuit. The simplest and most widely used form of track circuit is that in which (a source of electrical current is provided adjacent one end-f the track section, one terminal of the source being connected to one of the rails of the track section and the other terinitial being connected to theother rail. Adjacent the other end of the track section, an electrically responsive relay is provided, one terminal of which is connected to one of the rails of the track section and the other terminal to the otherrail. A closed electrical circuit, of which the rails of the track section form a part, is thereby established from the source of current to the track relay, which is thus normally retained in an energized condition; When a railway vehicle occupies the section of i a-ilway track provided with such a track circuit, the axles .and wheels of the vehicle forr'n aplurality of shunt paths which shunt or .short circuit the track. circuit current away from the relay thereby causing the relay to be deiene'rgized.

nronly referred to as front contacts and back contacts,

'res'pectively. Railway traffic controlling apparatus, such tionfof occupancy of the track section.

Track relays are provided with one or more electrical contacts some of which are closed when the relay is in an energized condition and some of which are closed "when the relay is deenergized. These contacts are com- "Under various conditions such as when the rails of attack section a're rusty orcovered wit-h afilm of insulattrig material such as sand, dust, etc. it has been found that there maybe a momentary loss of track circuit; shunt vi/hen a railway vehicle is moving through t -hetrack section; This loss of 'shunt will allow the traclc'relay to be momentarily energized andthe, detection of the presence of the vehiclein the track "section momentarily lost. This ,loss of detection of track occupancy may cause improper o eration of the traffic controlling apparatus, such as the momentary display of a proceed indication on a sig-.

when it should be displaying a stop indication, and

could result in an obviously dangerous condition.

Heretofore, the most satisfactory arrangements for providing protection against momentary loss of track circuit shunt made use of a capacitor or condenser con .nected across the terminals of a repeater relay which was. energized by a circuit through a back contact of the track relay. This arrangement provided the repeater relay with relatively long delayed release time. A second 0 repeater relay which was energized by acircuitthrou'gh Patented Sept. .1, 1959 2 a from cont'aet of the track relay and a back contact of the capaeitorfsnubbed relay was used for controlling the trafiic controlling apparatus. It is apparent that if the capacitor 'sho'uld become disconnected from the asso- 'ciated relay or if the capacitor should become defective in some manner, the desired delay time would not be obtained. One object of my invention, therefore, is to provide protection against momentary loss of track circuit shunt of means of improved and novel circuit arrange'rnents whereby a time delay is provided and a check is made to determine that the apparatus for providing the time delay is operative.

In practicing my invention I attain the above object and advantage by employing the charge time of an energy storing device or capacitor to delay the release time of a repeater rel-ay.- This repeater relay is energized by a circuit through a back contact of a. second repeater relay which is retained energized by a circuit through a front contact of the track relay and one of its own front con t acts. The energy stored in said capacitor is employed to reenergize the second repeater relay after the said release time of the first repeater relay has expired.

I shall describe three forms of apparatus embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawings:

Fig. l is a diagrammatic view showing one form of (track circuit apparatus embodying my invention.

ever, for the salte ofsimplicity the energy source is not shown in the drawings but its positive and negative terminals are identified in each of the figures of the drawings by the reference characters i3 and N, respectively. Similar reference characters refer to similar parts in each of the drawings.

7 Referring first to Fig. 1 of the drawings, a stretch of railway track is shown over which trains may move in either direction. The rails of the track stretch are designated by the reference characters land 1a and the stretch of track is divided at two points by insulated joints designated by a reference character 2 to form a track section designated by reference character TI This track section is provided with a track circuit which includes a source of current, here shown as a battery TB connected across the rails adjacent one end of the track section T, and a track relay designated TR connected across the rails adjacent the other end of the track section.

signal for governing movements of trains over the track 'secuon is located adjacent the insulated joints 2 at each end of the track stretch. The signal designated by the reference character 18 is for governing train movements to the right or in an eastward direction over the track section and the signal designated by the reference character 28 is for governing train movements to, the left or in a westward direction over the track section. These signals may be of any type such as the Well known color light or searchli'ghtsignals. i

.There is also shown in the drawing of Fig. 1 a first or back contact repeater relay designated by the reference character TBP, which relay is energized by a circuit through a back contact of the track relay TR, and through a ba'ckcontactof asecond or front contact repeater relay completely discharged condition. -.be traced from the left hand terminal of the-capacitor CD a. capacitor or energy storing device designated by the reference character CD. A resistor designated by the reference character R is used in series with the energy Relay TFP is retained in an energized condition by a second circuit through one of its own front contacts, its second winding, and a front contact of the track relay TR. Contacts of the second repeater relay TFP are used for control of the signals or traflic controlling apparatus in place of using contacts of the track relay for said control.

The signal control circuits shown have been shown only to the extent necessary to provide an understanding of my invention. It is suificient to point out that signals 18 and 28 will display a proceed indication when a circuit is completed through front contacts of the repeater relay TFP to the signal mechanism, and will display a stop aspect v or first repeater relay TBP is deenergized and front contact repeater or second repeater relay TFP is in aneuergized condition. Relay TFP is normally retained in an energized condition by a circuit which may be traced from 7 battery terminal B through front contact a of relay TFP,

upper winding of relay TFP, front contact a of trackv storing device CD. This resistor serves to lengthen the time required to charge and discharge capacitor CD.

relay TR to battery terminal N. The traffic controlling apparatus, signals 18 and 25 are shown normally displaying a proceed indication, signal 15 being controlled by a control circuit which may be traced from battery terminal B through front contact b of relay TFP and the winding of the control relay or mechanism for signal 18 to battery terminal N. Signal 25 is controlled by a similar circuit which may be traced from battery terminal B through front contact c of relay TFP and the winding of the control relay or mechanism for signal 28 to batback contacts a and b, respectively, closes an energizing circuit for relay TBP which may be traced from battery terminal B through back contact a of relay TFP, winding of relay TBP, and back contact b of trackrelay TR to battery terminal N. The closing of back contact a of relay TR closes a shunt circuit for the energy storing device or capacitor CD insuring that this device is in a This shunt circuit may through resistor R and back contact a of relay TR to'the right hand terminal of capacitor CD and battery terminal N. The energization of relay TBP and consequential closing of its front contact a also closes a second shunt circuit for capacitor CD. This shunt circuit 'may' be traced from the left hand terminal of capacitor- CD through resistor R, front contact a of relay TBP, back contact b of relay TR to the right hand terminaljof capacitor CD and battery terminal N. It is, therefore,

apparent that an arrangement is provided to insure that the energy storing device CD is completely discharged before the operational cycle which includes the 'use'of that device is initiated. The deenergization of relay TFP as described above opensthe control circuit to signals 18 and 2S at-front' contacts b and c of relay TFP, respectively. I Thesesignals the following described details.

are thereby caused to display a stop indication when a railway vehicle or train enters track section T.

When the said vehicle or train leaves track section T, relay TR will again become energized opening at back contacts a and b of that relay the above described shunt circuits for capacitor CD. This latter device is now, therefore, in condition to receive an energy storage. The opening of back contact b of relay TR also opens the previously described energizing circuit for relay TBP. However, relay TBP will not immediately drop as it is temporarily retained energized by a circuit which may be traced from battery terminal B through back contact a of relay TFP, winding of relay TBP, front contact a of relay TBP, resistor R, left hand terminal of energy storing device CD, and the right hand terminal of device CD to battery terminal N. Relay TBP will, therefore, remain energized until the charge on the capacitor CD has reached such a value that the charging current through the winding of relay TBP'is below the drop-away value of that relay. Whenthis degree of charge of capacitor CD is attained, relay TBP will be deenergized closing its back contact a. The deenergization of relay TBP completes an energizing circuit for relay TFP using the energy stored in the capacitor or energy storing device CD. This circuit may be traced from the left hand terminal of capacitor CD through the resistor R, back contact a of relay TBP, lower winding of relay TFP, and the front contact b of relayTR to battery terminal N. The energization of relay TFP again establishes the retaining circuit for that relay throughits own front contact a and front contact ll trol circuits to the trafiic controlling devices, signalslS and 2S, and they, again display a proceed aspect for another train to enter the track section.

I shall now assume that another train enters track section T deenergizing track relay TR and repeater relay TFP and energizing repeater relay TBP as previously de scribed. I shall further assume that there is a momentary loss of shunt of the track circuit for track section T so that relay TR is momentarily energized thereby momentarily opening the pickup circuit for relay TBP through the back contact [2 of relay TR. Under these conditions relay TBP will not immediately release due to the circuit for charging capacitor CD through the winding of relay TBP. When the track circuit shunt is again established, relay TR will again close the pickup circuit to relay TBP. Also the previously described shunt circuits for capacitor CD will be closed and the partial energy storage in the device CD will be discharged. Under conditions of a momentary loss of track circuit shunt it is apparent that relay TFP will not be energized to close the control circuits to signals 18 and 28 unless the loss of shunt is of sufiicient duration to allow capacitor erative. This is accomplished through the utilization of the charging time of a capacitor rather than the slow drop-away time of a relay having a capacitor snub on the winding thereof.

Fig. 2 of the drawings is identical to Fig. 1 except in In the drawing of Fig. 2 the first repeater relay TBP is provided with two windings. Energy stored in a second capacitor or energy storing device designated by the reference character CE is utilized for picking up of relay TBP by a circuit through a back contact of relay TFP. A resistor designated by the reference character RN is connected in series withthe-device CE for the same purpose that resister-R is used in series with capacitor CD. Relay .TFP is energized and retained energized in the sam ma'n nor as in Fig. 1. In the arrangement shown in Fig. 1,

.in the event track relay TR is inadvertently deenergized only long enough to open its front contact and deenergize relay TFP'but not long enough to close its back contact and energize relay TBP, relay TFP can not be reset. The modification of Fig. 2 insures the energiz'ation f relay TBP and the reset action of the apparatus. Such ,right hand terminal of capacitor CE, and left hand terminal of capacitor CE to battery terminal N. When a train enters track section T and deenergizes track relay TR, and consequently .relay TFP, a circuit is completed for energizing relay TBP by the energy stored in capacitor CE. This circuit may be traced from right hand terminal of capacitor CE through resistor RN,back contact d of relay TFP, and through the lower winding of relay TBP to battery terminal N. Relay TBP is thus energized and is retained energized by a circuit which may be traced from battery terminal B through back contact a of relay TFP, upper winding of relay TBP,

from contact a of relay TBP, and back contact I; of relay TR to battery terminal N.

When the train vacates track section T and relay TR is reenergized, relay TBP is momentarily retained energized until capacitor CD is charged by a circuit which may be traced from battery terminal B through back contact a of relay TFP, upper winding of relay TBP,

.front contact a of relay TBP and through resistor R to the left hand terminal of capacitor CD. Similarly, as in the arrangement of Fig. 1, when the charge in capacitor CD attains a point Where insufiicient energy is flowing through relay TBP to retain that relay energized, the relay will drop out and complete the energizing circuit to the lower winding of relay TF P. It is apparent, therefore, that the apparatus of Fig. 2 operates in a similar manner to that of Fig. 1, the trafiic controlling devices 18 and 28 being controlled over front contacts b and c of relay TFP.

Fig. 3 shows a modification of my invention similar to Fig. 2 except that one less contact on relay TFP and a rectifier or asymmetric unit designated by the reference character RE, is required. In this arrangement, the right hand terminal of capacitor CE is connected directly to battery terminal B and under normal conditions of the apparatus always has a charge of energy stored therein. The charging circuit for capacitor CE may be traced from battery terminal B to the right hand terminal of capacitor CE, left hand terminal of capacitor CE, through rectifier RE in its low resistance direction, and through resistor RN to battery terminal N. When relay TFP is deenergized due to the occupancy of track section T by a train, the charge of energy stored in capacitor CE is discharged through the lower winding of relay TBP by means of a circuit which may be traced from the right hand terminal of capacitor CE through back contact a of relay TFP and through the lower winding of relay T BP to the left hand terminal of capacitor CE. Resistor RN prevents a short circuit on the battery when the back contact of relay TFP is closed. Relay TBP is retained energized by a circuit which may be traced from battery terminal B through the upper winding of relay TBP, front contact a of relay TBP, and back contact b of relay TR to battery terminal N. When track relay TR is again energized, the operation of the apparatus is the same as in the modifications of Figs. '1 and 2. It should be pointed out that the rectifier or asymmetric unit RE used in the modification of Fig. 3 provides a circuit path for changing capacitor CE and also insures that the charge of energy stored in capacitor CE will flow through the lower Winding of relay TBP, the polarity of the charge being such that it is blocked from flowing from left to right through the unit RE to the "left-hand terminal of capacitor CE. 10

the modifications of my invention shown in Figs. 1, 2

'From the above description, it follows that in each of and 3. I have shown an arrangement for protection against momentary loss of track circuit shunt using the charging time of an energy storing device for providing a delayed pickup of the track repeater relay TFP and in which the integrity of the energy storing device and its associated circuits is checked before the energization of the track repeater relay TFP can be accomplished.

Although I have herein shown and described only a few forms of apparatus embodying my invention, it is to be understood that various changes and modifications ma'ybe made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

1. In combination with a section of railway track having a track circuit including a source of current and a track relay, a first repeater relay, a second'repeater, relay,

, an energy storing device, means including a back contact front contact of said second repeater relay for retaining said second repeater relay energized, and trafiic controlling apparatus controlled by a front contact of said second repeater relay.

2. In combination with a section of railway track having a track circuit including a source of current and a track relay, a first repeater relay, a second repeater relay, means including a back contact of said second repeater relay for energizing said first repeater relay, an energy storing device, means including a back contact of said track relay for discharging said energy storing device, means including a front contact of said first repeater relayfor charging said energy storing device and retaining said relay energized only until said energy storing device is charged; means including said energy storing device, a back contact of said first repeater relay and a front contact of said track relay for energizing said second repeater relay; means including a front contact of said track relay and a front contact of said second repeater relay for retaining said second repeater relay energized, and trafiic controlling apparatus controlled by a contact of said second repeater relay.

3. In combination with a section of railway track having a track circuit including a source of current and a track relay, a first repeater relay, a second repeater relay, means including a back contact of said second repeater relay for energizing said first repeater relay, an energy storing device means including a back contact of said track relay for retaining said first repeater relay energized and discharging said energy storing device; means including a front contact of said first repeater relay and effective only when said track relay is energized for charging said energy storing device and retaining said repeater relay energized until said energy storing device is charged; means including said energy storing device, a back contact of said first repeater relay and a front contact of said track relay for energizing said second repeater relay;

Having thus described my invention, what I claim means including a front contact of said track relay and 'a frontcontact of said second repeater relay for retaining said second repeater relay energized, and traffic controlling apparatus controlled by a contact of said second repeater relay. 4. In combination with a section of railway track having a track circuit including a source of current and a track relay, a first repeater relay, means including a back contact of said track relay for energizing said first repeater relay, an energy storing device, means including a front contactof said first repeater relay for charging .said energy storing device, a second repeater relay; means including said energy storing device, a back contact of said first repeater relay'and afront contact of said track relay for energizing said secondrepeater relayyrneans including a front contact of said track relay and a front contact of said second repeater relay for retaining said second repeater relay energized, andtraflic controlling apparatus controlled by a front contact of said secon repeater relay.

5. In combinationwith a section of railway track having a track circuit including a source of current and a 'track relay, a first repeater relay, a second repeater relay, an energy storing device, means including aback contact of said second repeater relay and a back contact of said track relay for energizing said first repeater relay, means including a front contact of said first repeater relay for charging said energy storingdevice; means in- -trolling apparatus controlled by a front contact of said second repeater relay.

6. In combination with a section of railway track having a track circuit including a source of current and a track relay, a first repeater relay, a second repeater relay,

a first energy storing device, a second energy storingde- -vice, means including a front contact of saidsecond repeater relay for charging said second energy storing dejvice, means including a back contact of-said second repeater relay and said second energy storing device for energizing said first repeater relay, means including a back contact of said second repeater relay and a front contact of said first repeater relay for charging said first energy storing device; means including said first energy storing device, a back contact of said first repeater relay and a front contact of said track relay for energizing said second repeater relay; means including a front contact of said track relay and a front contact of said second repeater relay for retaining said second repeater relay energized, and traflic controlling apparatus controlled by'a fron contact of said second repeater relay.

7. In combination with a section of railwaytrack having a track circuit including a source of current and a track relay, a first repeater relay, a second repeater relay, a first energy storing device, a second energy storing device, an asymmetric unit, a" circuit including said asymmetric unit for charging said second energy storing device; means including said second energy storing' device and a back contact of said second repeater relay for energizing said first repeater relay; means including a front contact of said first repeater relay for charging said first energy storing device; means including said first energy storing device, a back contact of said first repeater relay 7 and a front contact of said track relay for energizingsaid frontcoritact of :said second repeater relay.

References Cited in the file of this patent UNITED STATES PATENTS I Staples f Sept. 29; 1953 UNITED STATES PATENT OFFICE; CERTIFICATE OF CORRECTION Patent No. 2,902,593 September 1, 1959 Arthur E. Dodd It is hereby certified that error appears in the p inted specification of the above numbered patent requiring correction and that the said Letters Patent should readas corrected below.

Column 6, line 29, for "repeater, relay," read repeater relay, same column 6, .line 66, after "device" insert a comma.

Signed and sealed this 19th day of January 1960.

Attest:

KARL H. AXLINE Attesting Officer ROBERT C. WATSON Commissioner of Patents 

